The present invention stems from a discovery that certain enzymes lying next to the soybean surface, directly beneath the skin, causes a bitter flavor, and it was determined that it was necessary to debitter the bean so that the protein would not be denatured or in any way decomposed. By experimentation, it was determined that subjecting the beans to too high a temperature destroyed certain proteins therein so that neither the extracted liquid protein, or that remaining in the residue from the extract, would gel properly for use as a soybean curd or in meat analogs.
In addition, with too high a temperature, the full amount of suspendable protein would not extract from the ground bean slurry, and proper proportions of desired amino acids would not be left in the suspendable liquid protein.
It was discovered that the bitterness from these enzymes could be reduced in the suspendable extracted liquid protein by passing live steam through the liquid until the foam from this liquid was boiled down in open vessels, but the bitterness was never entirely absent from the end product. Also, the antitripson factor was not totally eliminated by this open vessel process.
Therefore, in an effort to completely eliminate the antitripson factors, it was proposed to pass live steam into a closed pressure vessel held at 10 P.S.I. for 10 minutes with a small vent cock open so as to assure that the heat was uniform in the entire vessel, after which the liquid protein was blown into a vented chamber. Bitterness was reduced to a greater degree than in the open chamber process. Furthermore, it was determined that continuing this pressure vessel heating for 10 minutes and then exhausting the liquid into a vacuum chamber, reduced the bitterness further. However, this method only helped to decrease the bitterness extracted in the liquid protein, and still left all of the bitterness in the fibrous residue containing considerable protein and fats with a high nutritional value.
In continued efforts to eliminate this bitterness, it was discovered that washing the dry bean in three or four waters somewhat reduced the bitterness. However, the required friction and rubbing of the bean, as well as the soaking, created heat which energized the enzymes so that the bitter flavor premeated the entire bean.
In a further effort, the dry bean was subjected to boiling or parboiling, but the heat rate was so slow that the enzymes were activated and released so that the bitterness permeated the entire bean. However, some reduction in bitterness resulted, but, at the same time, the ability to extract protein was reduced.
Continued efforts included soaking the beans until fully hydrated and then rapidly heating with live steam in an open vessel. The process of hydration created slow heat and activated the enzymes and resulted in bitterness permeating the entire bean. Although the live steam drove off some of the volatile oil and gases, no debittering of the bean resulted.
In addition to the foregoing, another method involved hydrating the beans until fully soaked, after which they were ground in a disintegrator with boiling water and steam being injected into the disintegrator. This tended to reduce the bitterness to a considerable degree, but had a tendency to gel part of the protein back into the fiber of the residue so that valuable amino acids were not left in the extractable protein and the residue would not gel, as desired, in meat analogs.
While various other methods have been proposed for treating soybeans and other nuts and fruits, such as those of U.S. Pat. Nos. to Darling 2,606,916, Steinkraus 3,721,569, Homann 4,024,168, and Grassl 4,035,194, none have been successful and satisfactory in destroying and expelling the enzymes lying next to the covering under the skin of the bean and retaining the beans in the dry state so that they can be shipped, stored, and used without the loss of protein, or being decomposed or injured for use in any beverage, meat analog, or byproduct.